JPH06250539A - Heating device - Google Patents

Abstract

PURPOSE:To shorten the feed or current carrying distance even when a material having a high volume resistance value is used to generate a sufficient heat, and perform a desired heating, by arranging feed electrodes on an electric heating element so that the polarity is alternately different from each other along the perpendicular direction to the advancing direction of a recording material. CONSTITUTION:An electric heating element 10 is formed on a heat resisting base 103 such as alumina, and comb-tooth electrodes 101, 102 having different polarities in right-angled directions to the recording material advancing direction on the electric heating element 100 are alternately arranged at equal intervals (h). An insulating layer 104 by glass is further formed on the electric heating element 100 and the electrodes 101, 102. The resulting heating body 9 is installed to a fixing device, and the current application from an AC power source 20 is controlled by a control device 15 on the basis of the information of a thermistor 8. By constituting the heating body 99 in this way, a fixed resistance value of the heating body can be provided, even when a material having an extremely high volume resistance is used, by changing the electrode distance or heating segment length (h).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to heating a heat-resistant film in contact with a heating body which generates heat by energizing, and bringing a material to be heated into close contact with the surface of the film opposite to the heating body. The present invention relates to a film heating type heating device which passes a body position and applies heat energy from a heating body to a material to be heated through the film.

[0002]

2. Description of the Related Art A heating device of the film heating type as described above is disclosed in Japanese Patent Laid-Open No. 63-31318 proposed by the present applicant.
The image heating fixing device in the image forming apparatus such as the electrophotographic copying machine, the printer, the fax, etc., that is, the image for the electrophotography, electrostatic recording, magnetic recording, etc. Direct or indirect (transfer) to the surface of the recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) by using a developing material (toner) made of heat-meltable resin by the forming process means. It can be utilized as an image heating and fixing device that heats and fixes, as a fixed image, an unfixed developer image corresponding to the target image information, which is formed by the method, as a fixed image.

Further, it can be used, for example, as an apparatus for heating a recording material carrying an image to modify the surface properties of gloss and the like, an apparatus for post-treatment, etc.

More specifically, a thin heat-resistant film (sheet), a means for moving the film, and a heating element (heater) arranged to be fixedly supported on one side of the film with the film inside. And a pressure member disposed on the other surface side so as to be opposed to the heating body and closely contacting the developer image carrying surface of the recording material to be image-fixed to the heating body through the film, At least during image fixing, the film is moved at the same speed in the forward direction as the recording material to be image-fixed, which is conveyed and introduced between the film and the pressure member, and the running moving film is sandwiched between the film and the heating member. By passing through a fixing nip portion as a fixing portion formed by pressure contact with a pressure member, the developer image carrying surface of the recording material is heated by the heating body through the film to form an unfixed developer image. Thermal energy is applied to the (unfixed toner image) to soften it. · Allowed melt, then an image heating fixing apparatus of film heating type which is based on that to separate the recording material and the film after fixing portion passing through at the separation point.

FIG. 12 shows a plan view of a heating body used in the above-mentioned image heating and fixing device with a partly omitted and partially cutaway plan view and a block diagram of an energization control system.

The heating element 2 of this example is composed of a. An elongated ceramic substrate 3 having electrical insulation, heat resistance, and low heat capacity, such as Al ₂ O ₃ (alumina), AlN, or SiC, whose longitudinal direction is substantially orthogonal to the moving direction of the heat resistant film 3.
And b. The substrate 3 is formed in a linear shape or a strip shape along the length of the substrate in the central portion of the one surface side (front surface side) in the substrate width direction,
An electric heating element 4 such as silver palladium (Ag / Pd) as a heat source, and c. The power supply electrodes 5, 6, 6'and the through holes 5 formed on the surface of the substrate by electrically connecting both ends of the energization heating element 4 respectively.
0, and d. An electrically insulating overcoat layer 7 of glass or the like as a surface protective layer covering the surface of the substrate 3 on which the electric heating element is formed, and e. It comprises a temperature detecting element 8 such as a thermistor provided in contact with the other surface side (back surface side) of the substrate 3, a temperature fuse 9 serving as a temperature detecting element (thermal protector) for safety measures, and the like.

The overcoat layer 7 side of the heating element 2 is the film contact sliding surface side, and this surface side is exposed to the outside to fix the heating element 2 to a supporting portion (not shown) through a heat insulating heater holder 13. I am allowed.

The heating element 2 is a power supply electrode 5 at both ends of an electric heating element 4.
A voltage is applied from the AC power supply 20 between 6 and the energization heat generating body 4 generates heat to raise the temperature.

The temperature of the heating element 2 is detected by the temperature detecting element 8 on the back surface of the substrate, and the detected information is fed back to the energization control device 15 to control the energization from the AC power source 20 to the energization heating element 4 to fix the heater. Temperature control is performed so that the temperature of the heating element 2 detected by the temperature detection element 8 at the time of execution becomes a predetermined temperature (fixing temperature).

The temperature control of the heating element 2 is performed by controlling the applied voltage or current to the energization heating element 4 or by controlling the energization time. Methods for controlling the energization time include zero-cross wave number control for controlling energization and non-energization for each half-wave of the power supply waveform, and phase control for controlling a phase angle energization for each half-wave of the power supply waveform.

That is, the output of the temperature detecting element (thermistor) 8 is A / D exchanged and taken into the CPU, and based on the information, the energization heating element 4 is energized by an SSR (solid state relay) having a triac or the like. The AC voltage is subjected to pulse width modulation such as phase control or wave number control to control the energization of the energization heating element 4 so that the temperature detected by the temperature detecting element 8 of the heating element is constant.

The temperature fuse 9 is connected in series to the energization path for the energization heating element 4 and is arranged close to or in contact with the back surface of the substrate 3 of the heating element 2, so that energization control of the energization heating element 4 is impossible. When a situation occurs and the temperature of the heating element 2 rises abnormally (runaway of the heating element), the thermal fuse 9 is activated and the energization heating element 4 is activated.
The energization circuit is released to turn off the energization of the energization heating element.

The film heating type apparatus as described above is
Since the heating element 2 having a low heat capacity can be used, the weight time can be shortened (quick start property) as compared with the conventional heating device such as a heat roller system, and the quick start can be performed. Preheating when not in use is not necessary, and power saving can be achieved in a comprehensive sense. In addition, it has an advantage that it can solve various drawbacks of other heating type devices, and is effective.

[0014]

The resistance material used for the electric heating element of the heating element is generally a noble metal type material such as Ag / Pd and is very expensive.

Even if an attempt is made to reduce the cost by replacing it with a cheaper material, such a material cannot be used conventionally because of its high volume resistance value.

That is, the heating element needs to generate enough electric power to rise above a certain temperature within a limited time. On the other hand, the power source supplied to the heating element is usually a commercial power source (AC100 / 200V), and its voltage is constant. Therefore, the resistance value of the heating element must be below a certain value.

The resistance value of the heating element is determined by the thickness, width (recording material passing direction), length (direction perpendicular to the recording material passing direction), and volume resistance of the heating element. Regarding the length, it is almost the same as the width of the recording material and is constant, and regarding the width of the electric heating element, expanding the width of the nip is not effective because the heat of the portion protruding from the nip is not transferred to the recording material. Even if the thickness of the heating element is increased, there is a limit from the manufacturing method such as screen printing.

That is, in order to reduce the resistance value of the heating element to a certain value or less, it is necessary to set the volume resistance value of the current-carrying heating element to a certain value or less. It was impossible to use.

[0019]

According to the present invention, a material having a high volume resistance value is provided by arranging power supply electrodes on an electric heating element so as to have different polarities alternately along a direction perpendicular to the recording material traveling direction. Also in the case of using, it is possible to perform sufficient heat generation and desired heating by shortening the power supply or energization distance.

[0020]

1 and 2 show a heating device according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a heat-resistant film (fixing film) in the form of an endless belt, which is a driving roller 11 arranged substantially parallel to each other, a driven roller 12 also serving as a tension roller, and a heating member (heater) 99. It is stretched between them.

The film 1 has a total thickness of 100 μm or less, preferably 40 μm or less and 20 μm or more in order to reduce the heat capacity and improve the quick start property, such as heat resistance, releasability, strength and durability. PTFE with
It is a single layer film of PFA or a composite layer film in which the surface of a film of polyimide, polyamideimide, PEEK, PES, PPS or the like is coated as a release layer of PTFE, PFA, FEP or the like.

Numeral 13 is a heater holder which heat-insulates and supports the heating element 99, and 10 is a film 1 sandwiched between the heating element 99 and the heating element 99. The film is pressed against the surface of the heating element 99 at a total pressure of 4 to 15 kg. The pressure roller has a rubber elastic layer having good moldability.

By rotating the driving roller 11, the film 1 is brought into close contact with the surface of the heating body 99 in the clockwise direction indicated by the arrow at least during image fixing, and slides on the surface of the heating body at a predetermined peripheral speed, that is, not shown. The recording material P, which carries the unfixed toner image T conveyed from the image forming section (A) side, is rotationally driven without wrinkles at substantially the same peripheral speed as the conveying speed.

The heating element 99 is an energization heating element (resistive heating element) 1 as a heat source that generates heat by supplying electric power as described later.
00, and the temperature is raised by the heat generated by the electric heating element 100. The electric heating element 100 is provided on the substrate 103.

While the heating element 99 is heated by the power supply to the electric heating element 100 and the film 1 is rotationally driven, the pressure contact portion N (fixing nip portion) between the heating element 99 and the pressure roller 10 is By introducing the recording material P between the film 1 and the pressure roller 10, the recording material P
Adheres to the film 1 and passes through the pressure contact portion N in an overlapping state with the film.

Heat energy is applied to the recording material P from the heating body 99 through the film 1 in the process of passing through the pressure contact portion, and the unfixed toner image T on the recording material P is heat-melted and fixed.
The recording material P is separated from the film 1 after passing through the pressure contact portion N and discharged.

In FIG. 2, a heat resistant substrate 10 made of alumina or the like.
An electric heating element 100 is formed on the electric heating element 3, and comb-shaped electrodes 101 and 102 having different polarities are alternately arranged at equal intervals h in the direction perpendicular to the recording material traveling direction on the electric heating element.
Further, an insulating layer 104 made of glass is formed on the energization heating element 100 and the electrodes 101 and 102 by coating.

The heating element 99 is mounted on the fixing device shown in FIG. 1, for example, and the controller 15 controls the energization from the AC power source 20 based on the information from the thermistor 8. That is, the controller 15 A / D converts the output of the temperature detection element 8,
It is taken into the CPU, and based on the information, the AC voltage applied to the energization heating element 4 is subjected to pulse width modulation such as phase control or wave number control by an SSR (solid state relay) having a triac etc. The energization of the energization heating element 4 is controlled so that the detected temperature of the body becomes constant.

When the heating element has such a structure, even if a material having a very high volume resistance such as RuO ₂ is used, the resistance value of the heating element can be kept constant by changing the electrode interval or the length h of the heat generating segment. You can get it.

The materials of the electrodes 101 and 102 are A in order to prevent a circuit short circuit due to electromigration.
It is desirable to use Ag / Pt, Ag / Pd, Au, Pt or the like that is less likely to migrate than g or the like.

If the junction width j of the electrodes 101 and 102 with the energization heating element 100 is a non-heat generating portion, if the width is too wide, fixing failure becomes a vertical stripe on the recording material. To prevent this, the joint width j is preferably about 1 mm or less.

Further, the electrodes 101 and 102 and the electric heating element 1
As shown in FIG. 3, if the joint with 00 is outside the width 1 of the heating element, it is not necessary to form a non-heat-generating portion locally within the width 1 of the heating element. Therefore, a large current can flow even if the electrodes 101 and 102 have a large width j.

Further, in order to compensate for the heat radiated from the electrodes 101 and 102, the energization heating element portion is extended so as to generate heat to some extent outside the energization heating element width 1 as shown by α in FIG. 4, and FIG.
It is also possible to locally increase the amount of heat generation by squeezing the current-carrying heating element at the electrode bonding position, as in the β portion and the γ portion in FIG.

By using a material having a large positive temperature resistance characteristic for the current-carrying heating element, it is possible to prevent non-sheet-passing temperature rise.

That is, when a recording material having a width smaller than the maximum paper passing width of the heating device is used, the heat radiation amount, that is, the heat generated by the recording paper, is the same even though the heat generation amount is the same in the paper passing region and the non-paper passing region. Because the heat is dissipated between the part where the heat is removed and the part where it is not, the temperature on the non-sheet passing side becomes high (the sheet passing area side is controlled by the thermistor 8 to be a constant temperature).
Therefore, if it happens frequently, the film on the non-sheet passing area side,
Such as a pressure roller. This causes a problem that the member deteriorates due to the high temperature.

Therefore, the energizing heating element is made of a material having a large positive temperature resistance characteristic (TCR), and when the temperature rises in the non-sheet passing portion, the resistance value of that portion rises and the calorific value is lowered. It is possible to reduce the non-sheet passing temperature rise.

That is, as shown in FIG. 7, the comb-teeth electrodes 101 and 102 are alternately arranged at equal intervals h on the energization heating element 300 having a large positive temperature resistance characteristic (preferably about 1000 PPM / ° C. or more). . At this time, each heat generating segment (the portion of the energizing heat generating body having the length h sandwiched between electrodes of different polarities) has the same resistance value. As the material of the electric heating element, for example, RuO ₂ mixed with Au can be used, and the TCR is about 4000 PPM / ° C.

The heating element 298 is constructed as follows. An electric heating element 3 is formed by a thick film paste containing RuO ₂ + Au on a heat-resistant ceramic substrate 299 such as Al ₂ O ₃ or AlN.
00 is printed by screen printing.

The thick film paste is RuO ₂ powder or Au powder having a diameter of 50 μm or less for imparting conductivity, and glass such as boron silicate or aluminum silicate for adhering to the ceramic substrate, Bi ₂ O ₃ , PbO. , ZnO, CaO,
This is a mixture of an inorganic binder powder mixed with an additive such as CuO, an organic binder such as ethyl cellulose for imparting a paste-like fluidity, and a high boiling point solvent such as terpineol and butyl carbitol.

The commercially available RuO ₂ thick film paste is TCR
Is about 100 PPM / ° C., and TCR 4000 PPM / ° C. is obtained by mixing Au with high TCR with this.

Next, the substrate on which the electric heating element is printed is dried and baked at a high temperature to burn off the solvent and the organic binder, and the inorganic binder is melted to bond the electric heating element to the ceramic substrate.

Next, Au, Ag, Ag / Pd, Ag / P
The electrodes 101 and 102 are printed and baked by screen printing using a thick film paste of t or the like to form the electrodes.

Further, a glass coat as an insulating layer (not shown) is formed on the electric heating element and the electrodes. The glass coat is also formed by screen-printing a thick film paste and firing.

In the heating element 298, the control circuit 15 controls the power supply 20 so that the temperature of the thermistor 8 provided on the back side of the substrate 299 of one heating segment becomes constant.

Now, when the recording material 297 having a width Y smaller than the maximum sheet passing width X of the heating element 298 is passed, the temperature Q1 in the non-sheet passing area rises due to the difference in heat radiation load. Then, the resistance value Q2 of the heat generating segment in the non-sheet passing area increases. Since the heat generation amount of each heat generation segment is determined by V ² / R (V: voltage between electrodes 101 and 102, R: resistance value of each heat generation segment), the heat generation amount Q3 of the heat generation segment in the non-sheet passing area decreases,
The temperature Q4 is reduced to reduce the temperature rise in the non-sheet passing area.

At this time, the length h of the heat generating segment is large,
Further, when the recording material edge e comes between the electrodes 101a and 102a as shown in FIG. 8, the heat generation amount per unit length of the area f is reduced, the temperature is lowered, and fixing failure occurs. That is, the area f
When the recording material 297 passes through the set, the temperature k1 in the non-sheet passing area increases and the resistance value k2 per unit length increases (the area f, which is the sheet passing area, has no temperature change, so the resistance value per unit length). No change). The calorific value per unit length is I ² r
Since (I is a current between 101a and 102a, r is a resistance value per unit length), the heat generation amount per unit length of the region f is smaller than the heat generation amount per unit length of the region g. However, since the total resistance value between the electrodes 101a and 102a increases, the electrode 1
Since the total current value flowing between 01a and 102a decreases,
The heat generation amount k3 per unit length of the region f decreases, and the temperature k
4 deteriorates, causing poor fixing.

The above is the case where the thermistor 8 exists in the paper passing area other than the heat generating segment (area f + g) where the recording material edge e exists.

As shown in FIG. 9, when the thermistor 8 exists in the sheet passing area (area f) of the heat-generating segment where the recording material edge e exists, the temperature is controlled by the thermistor 8 in the area f, so that fixing failure occurs. However, this time, the temperature S4 of the other heat generating segment in the paper passing area rises, causing a problem such as high temperature offset. Also, the recording material edge e
The amount of heat generated in the non-sheet passing area of the heat generating segment where is present becomes extremely large, causing thermal deterioration of the film, pressure roller and the like. This problem disappears when the length h of each heat-generating segment is sufficiently short, and preferably less than about 20 mm. That is, the heat unevenness generated in the paper passing portion and the non-paper passing portion of the heat generating segment having the recording material edge is alleviated by the heat conduction in the longitudinal direction of the heating element or its peripheral members (perpendicular to the recording material advancing direction), and the temperature difference does not occur. Because.

As in the heating element 400 of FIG. 10, A
3, B4, A4, etc. end of recording material of each size is connected to electrodes 101, 1
02 and the position of the comb-teeth portion of the heating element 401 do not cause the above-mentioned problems even if the heating segment length h is long. This is because all the above-mentioned problems occur because the paper passing area and the paper non-passing area are mixed in one heat generating segment, and the recording material end is the heat generating segment end, that is, the feeding electrode 10.
This is because there is no paper non-passage area in one heat generation segment if it is at the joint between the heat generating element 401 and the heat generating element 401.

In the heating element 500 of FIG. 11, the lengths T ₁ , T ₂ and T ₃ of the heat generating segments are not constant. The length of each heat generation segment is T3 for A4 size, T ₂ +
T ₃ is B4 _{size, T 1 + T 2 + T} 3 is compatible with various types of recording material width as that A3 size. Further, each heating segment is provided with an electric heating material having the same volume resistance value and the same thickness. The widths W ₁ , W ₂ and W ₃ of the heat-generating segments are adjusted so that the heat generation amount per unit length in the longitudinal direction of the heating element is the same.

The calorific value per unit length is

[0052]

[Equation 1]

Therefore, W ₁ : W ₂ : W ₃ = T ₁ ² : T
₂ ^2: is equal to the amount of heat generated per unit length of each heating segment as T ₃ ^2.

In FIG. 11, the same body is used for each heat generation segment.
The heat generation amount per unit length when using a product resistance value material
In order to equalize the width (W₁ , W
₂ , W ₃ ) Was changed, but the volume resistance was changed for each heat generation segment.
Width of each heating segment using heating element materials with different resistance values
May be equal.

The thickness of each heat generating segment may be changed.

Further, if it is rare to use a recording material having a width smaller than A4 size for the heating element of FIG. 11, a heating element material having a small temperature resistance characteristic may be used only for the T ₃ heating segment of FIG. This is because the non-sheet passing area rarely occurs in the heat generation segment having the length T ₃ , the non-sheet passing temperature rise occurs only for a short time, and the damage to the film, the pressure roller and the like is small. .

In the above embodiment, the electrodes 101, 1
02, etc., instead of distributing to both sides of the heating element 100, etc.,
It is also possible to collectively arrange them on one side.

[0058]

As described above, according to the present invention, the power supply electrodes are arranged in the current-carrying heating element so that the polarities are alternately different along the direction perpendicular to the recording material advancing direction. Even a high material enables a desired amount of electricity.

Further, by using a material having a positively large TCR for the electric heating element, the temperature rise in the non-sheet passing portion is reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a heating device according to an embodiment of the present invention.

FIG. 2 is a plan view of a heating body that is an embodiment of the present invention.

FIG. 3 is a detailed view of an example of an electrode joint portion of a heating body which is an embodiment of the present invention.

FIG. 4 is a detailed view of another example of the electrode joint portion of the heating body according to the embodiment of the present invention.

FIG. 5 is a detailed view of still another example of the electrode joint portion of the heating body according to the embodiment of the present invention.

FIG. 6 is a detailed view of another example of the electrode joint portion of the heating body according to the embodiment of the present invention.

FIG. 7 is an operation explanatory diagram showing that non-sheet passing temperature rise is improved by the embodiment of the present invention.

FIG. 8 is an explanatory diagram for explaining the operation of the embodiment of the present invention.

FIG. 9 is another explanatory diagram for explaining the operation of the embodiment of the present invention.

FIG. 10 is a plan view of one of the heating elements according to the embodiment of the present invention.

FIG. 11 is another plan view of the heating body according to the embodiment of the present invention.

FIG. 12 is a view for explaining a conventional method of energizing a heating element.

[Explanation of symbols]

99,298,400,500,2 ... Heating body 100,200,202,201,203,300,4
01, 503, 4 ... Electric heating element 101, 102, 501, 502, 5, 6, 6 '... Electrode 104, 7 ... Insulating layer 15 ... Control circuit 20 ... Power supply 103, 299,
3 ... Substrate 8 ... Thermistor 13 ... Heater holder h ... Electrode spacing j ... Electrode bonding width l ... Electric heating element width 297, P ... Recording material Y ... Recording material width X ... Maximum sheet passing width e ... Recording material end 9 ... Thermal fuse 50 ... Through-hole 1 ... Film 10 ... Pressure roller N ... Nip T ... Toner 11 ... Drive roller 12 ... Driven roller

Claims (4)

[Claims] 1. A heating body, and a heat-resistant film having one surface in contact with the heating body and slidingly contacting the other surface with the heating body, and the film and the heating body move together on the heating body. In a heating device that transfers the heat of a heating element to an object to be heated, the heating element is composed of at least an energization heating element and an electrode that supplies power to the energization heating element, and the electrode advances to the heating element to the energization heating element. A heating device characterized in that the polarities are alternately arranged along the direction perpendicular to the direction. 2. The heating device according to claim 1, wherein the electric heating element has a positive resistance temperature characteristic. 3. The resistance temperature characteristic is about 1000 PPM /
The heating device according to claim 2, wherein the heating device has a temperature of not less than 0 ° C. 4. The heating device according to claim 2, wherein the electrode positions of the electric heating element coincide with the end positions of various objects to be heated.